Anti-Thyroglobulin IgG in Therapeutic Immunoglobulins: A Reactivity Bias in IgG4 Subclass

Abstract

Therapeutic immunoglobulins are used in the treatment of immunodeficiencies as well as several autoimmune and inflammatory diseases. These intravenous immunoglobulins (IVIg) represent the healthy human IgG repertoire, which can be reactive for both self and non-self antigens. A bet-ter characterization of IVIg's repertoire is an important aspect to enable its effective utilization as an immunomodulatory treatment. In this study we have investigated the reactivity of IgG1, IgG2, IgG3 and IgG4 present in IVIg for a small selection of antigens, including actin, DNA, ferritin and thyroglobulin. We observed that two commercial preparations of therapeutic immunoglobulins contain very high reactivity for thyroglobulin, which was predominantly detected by IgG4. Since IgG4 antibodies can have immunomodulatory properties, these result suggest that these anti-thy-roglobulin may have a role in the IVIg treatment of autoimmune disease characterized by high avidity for anti-thyroglobulin antibodies such as Hashimoto's disease.